1. Field of the Invention
The present invention relates to a process for fabricating a wiring board. More particularly, the present invention relates to a process for fabricating an embedded circuit board.
2. Description of Related Art
Embedded circuit boards are developed according to a current wiring board technique, and circuits on a surface of such wiring board are embedded in a dielectric layer, and are not protruded out from a surface of the dielectric layer.
FIG. 1A to FIG. 1E are cross-sectional views illustrating a fabrication flowchart of a conventional embedded circuit board. Referring to FIG. 1A, a method for fabricating the conventional embedded circuit board includes following steps. First, a copper metal layer 114a and a copper wiring layer 116a are sequentially formed on a carry substrate 112a to form a wiring carrying substrate 110a. 
Referring to FIG. 1B, the wiring carrying substrate 110a is laminated on another wiring carrying substrate 110b via a prepreg, wherein a structure of the wiring carrying substrate 110b is the same to that of the wiring carrying substrate 110a. In detail, the wiring carrying substrate 110b also includes a carry substrate 112b, a copper wiring layer 116b and a copper metal layer 114b located between the copper wiring layer 116b and the carry substrate 112b. After the wiring carrying substrate 110a is laminated on the wiring carrying substrate 110b, the prepreg is cured to form a dielectric layer 120.
Referring to FIG. 1B and FIG. 1C, the carry substrate 112a and the carry substrate 112b are removed to remain the copper metal layers 114a and 114b, and the copper wiring layers 116a and 116b. Next, a mechanical drilling process and a plating through hole (PTH) process are sequentially performed to form a conductive through hole structure T1. When the conductive through hole structure T1 is formed, a copper plating layer 130a and a copper plating layer 130b are respectively formed on the copper metal layer 114a and the copper metal layer 114b. 
Referring FIG. 1C and FIG. 1D, etching is performed to remove the copper plating layers 130a and 130b, and the copper metal layers 114a and 114b. Next, ink material 140 is filled into the conductive through hole structure T1.
Referring to FIG. 1D and FIG. 1E, after the ink material 140 is filled, a solder mask layer 150a is formed on the copper wiring layer 116a, and a solder mask layer 150b is formed on the copper wiring layer 116b. By such means, fabrication of the conventional embedded circuit board 100 is completed.
In the current wiring board technique, the embedded circuit board has a development trend of high-density layout and fine lines. However, during the process of laminating the wiring carrying substrate 110a to the wiring carrying substrate 110b (referring to FIG. 1B), the prepreg is deformed due to a press, which is referred to as shrink-swell in the art. Such deformation can generally change a whole dimensional scale of the embedded circuit board 100, and can also change a layout of the copper wiring layers 116a and 116b and a relative position of the conductive through hole structure T1.
In the current wiring board technique, a kind of the deformation generated during the laminating process can change the relative position between the layouts of the copper wiring layers 116a and 116b (which is also referred to as layer-layer shifting in the art). Though, the deformation that causes such layer-layer shifting can be properly controlled via a positioning apparatus of a lamination device, and a relative shifting amount thereof can be below 25 μm. Therefore, influence of the deformation generated due to the layer-layer shifting caused by the laminating process is greatly reduced.
The higher the layout densities of the copper wiring layers 116a and 116b are, the greater the shrink-swell deformation influences the layout of the copper wiring layers 116a and 116b, and the relative position of the conductive through hole structure T1. During the mechanical drilling, since the layouts of the copper wiring layers 116a and 116b are changed, when a Muraki tooling system is applied, the through hole generated based on the mechanical drilling process is shifted, and even broken out (for example, the conductive through hole structure T2 in FIGS. 1C-1E).
The mechanical drilling process is taken as an example in the aforementioned conventional technique, though for the conductive blind via generated based on a laser drilling technique, the break out phenomenon, the positioning apparatus and the positioning principle are all the same to that of the mechanical drilling process, and even the rejection and a reason of the rejection are all similar, and therefore detailed description thereof is not repeated.